Buried n-doped semiconductor zones are required as so-called buffer zones or field stop zones for example in vertical power components such as power IGBT, power diodes, power thyristors or power MOSFET. Components having n-doped (field stop) zones that are buried, that is to say arranged at a distance from a surface of a semiconductor body, are described, for example, in DE 100 53 445 C2, DE 102 43 758 A1, EP 0 594 049 A1 or DE 102 07 522 A1. The function and the advantages of field stop zones in power components are described, for example, in Niedernostheide, F.-J. et al.: “13 kV Rectifiers: Studies on Diodes and Asymmetric Thyristors”, Proceedings ISPSD 2003 (Cambridge, UK), pages 122-125 or in DE 198 29 614 A1.
Buried field stop zones can be produced, for example, by means of sufficiently known epitaxy methods for depositing doped semiconductor layers successively on a semiconductor substrate the doping of which layers is chosen such that the desired doping profile is achieved in the resulting semiconductor body.
A further possibility for producing a buried n-doped semiconductor zone consists in producing the semiconductor zone as a doped zone of a first semiconductor body that is near the surface, which may be effected, for example, by means of a diffusion method during which dopant atoms are indiffused into the semiconductor body. The doped semiconductor body is subsequently connected to a second semiconductor body at the doped side, which results in a semiconductor body having a buried doped semiconductor zone. So-called wafer bonding methods are suitable for connecting the semiconductor bodies.
Both epitaxy methods and wafer bonding methods have the disadvantage of being complicated and therefore expensive. The wafer bonding method furthermore has the disadvantage that the charge carrier life time in the connected semiconductor body is significantly reduced in the region of the interface between the two original semiconductor bodies, which may adversely affect the function, in particular the turn-off behavior, of a component having a buried zone produced in this way.
DE 102 43 758 A1 describes producing a buried field stop zone by means of proton irradiation and a subsequent annealing step at temperatures of between 250° C. and 500° C. By means of the proton irradiation, on the one hand, defects are produced in the semiconductor body and, on the other hand, hydrogen is thereby introduced into the semiconductor body, hydrogen-induced donors or hydrogen-correlated donors arising from the defects and the hydrogen during the annealing step. The doping profiles produced by such a method essentially follow the distribution of the primary defects caused by the irradiation. The distribution has a Gaussian profile in the irradiation direction, the half value width in the case of proton irradiation being comparatively narrow, which results in a narrow doped zone in the case where only one irradiation energy is used.